Let's look at all the options in turn:
Impose stricter divisions of labor
-this doesn't have anything to do with trade, so it's not the correct answer.
Increase production quotas
-what we want is a bigger trade, not production, so again, not the correct answer
Loosen certain trade regulation
-this is the best answer. Loosening trade regulations will increase trade, but country A won't do it since it would challenge their control over the market
Permit limited private ventures
-in country B those are likely already permitted anyway
